Novel terpolyamides of aliphatic and aromatic acids and process



United States Patent 3,383,369 NOVEL TERPULYAMIDES 0F ALIPHATIC AND AROMATIC ACIDS AND PRGCESS James S. Ridgway, Durham, N.C., assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed May 24, 1965, Ser. No. 458,430 4 Claims. (Cl. 260-78) ABSTRACT OF THE DISCLOSURE Terpolyamides having high boiling water shrinkage are composed of (A) 1 to 98 mole percent of hexarnethylene adipamide, (B) 1 to 98 mole percent of hexamethylene S-t-butylisophthalamide and (C) 1 to 50 mole percent of hexamethylene terephthalamide. These terpolyarnides are useful in the production of yarns, fabrics, films, textile fibers and reinforcing cords.

Polyamides, such as polyhexamethylene adipamide (nylon 66) and polycaproarnide (nylon 6) are well known in the art and have found significant commercial success both as textile fibers and as reinforcing fibers, such as tire cord. Although the textile fibers obtained from the previously known fiber-forming polyamides heretofore known are of great value, much research effort is being continuously expended in order to improve their properties. For example, these previously known polyamides all possess a relatively low shrinkage value, that is, the amount of shrinkage that occurs in fibers made from these polyamides when they are treated with boiling water is relatively small. In some commercial uses, for example, as hosiery, it is desirable that the polyamide textile fibers have increased shrinkage. Furthermore, in the production of conjugate fibers, that is, a fiber having two or more components, it is extremely desirable that at least one of the components have a relatively high boiling Water shrinkage. This is necessary in order that the crimp in a conjugate fiber be significant and permanent.

While, as pointed out above, previously known polyamides have found significant use in the reinforcement of rubber articles such as vehicle tires, an inherent drawback in their use to reinforce vahicle tires is their tendency to flatspot. Flatspotting is a term used to describe the out-of-roundness that occurs When a polyamide reinforced vehicle tire is allowed to rest for a period of time. That portion of the tire which is in contact with the pavement becomes flattened and, when the vehicle is started again this fiat spot causes vibration of the vehicle. While this phenomena of fiatspotting is not completely understood, there is at present a great deal of effort being put into finding a solution of this problem as regards polyamide tire cords.

It is an object of this invention to provide a novel terpolyamide.

It is a further object of this invention to provide a novel synthetic linear fiber-forming terpolyamide which has increased boiling water shrinkage characteristics.

It is a further object of this invention to provide a novel synthetic linear terpolymer from S-t-butylisophthalic acid.

It is a still further object of this invention to provide a terpolyamide from S-t-butylisophthalic acid which shows a reduced tendency to fiatspot when used as a reinforcing fiber in rubber vehicle tires.

It is a still further object of this invention to provide a textile fiber composed of this novel synthetic linear fiberforming terpolyamide.

It is a still further object of this invention to provide a process for producing a novel synthetic linear fiber-forming terpolyamide.

These and other objects will become apparent from the description given hereinafter.

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The terpolyamides of the present invention are useful in the production of shaped articles by extrusion, molding or casting in the nature of yarns, fabrics, films, pellicles, bearings, ornaments or the like. They are particularly useful in the production of textile fibers and as reinforcing cords produced therefrom.

The present invention provides a novel linear fiberforming terpolyamide composed of (A) l to 98 mole percent, based on the molecular weight of the polyamide, of units represented by the structure H I (OH2)BI I( J(CI-IQ)i-C J (B) 1 to 98 mole percent, based on the molecular weight of the terpolyamide, of units represented by the structure II rt 0 0 II II o IIO In a typical preparation, the terpolyamide is formed by interpolymerizing (A) substantially equimolecular proportions of adipic acid and hexamethylene diamine, (B) substantially equimolecular proportions of S-t-butylisophthalic acid and hexamethylene diamine and (C) substantially equimolecular proportions of terephthalic acid and hexamethylene diamine wherein component (A) is present in an amount sufficient to provide 1 to 98, preferably 30 to 60 mole percent of the final terpolymer, component (B) is present in an amount sufiicient to provide 1 to 98, preferably 10 to 50 mole percent of the final terpolymer and component (C) is present in an amount sufficient to provide 1 to 50, preferably 20 to 50 mole percent of the final terpolymer. It is, of course, obvious that the total mole percentage Will not exceed 100 percent. It will be understood that the designation equimolecular proportions of the diamines and the diacids includes the preformed salt reaction products thereof.

The terpolyamides of this invention are prepared by procedures well known in the art and commonly employed in the manufacture of simple polyamides. That is, the reactants are heated at a temperature of from C. to 300 C. and preferably from 200 C. to 295 C. until the product has a sufficiently high molecular weight to exhibit fiber-forming properties, which properties are reached when the terpolyamide has an intrinsic viscosity of at least 0.4. The reaction can be conducted at super atmospheric, atmospheric or subatmospheric pressure. Often is is desirable, especially in the last stage of the reaction, to employ conditions, e.g. reduced pressure, which will aid in the removal of the reaction by-products. Preferably, the reaction is carried out in the absence of oxygen, for example, in an atmosphere of nitrogen.

Intrinsic viscosity as employed herein is defined as Lim 10 c r N in which N is the relative viscosity of a dilute solution of the polymer in m-cresol in the same units at the same temperature and C is the concentration of grams of polymer per 100 cc. of solution.

The amount of component (A) present in the terpolymers of the present invention ranges from 1 to 98, preferably 30 to 60 mole percent, based on the molecular weight of the terpolymer. Component (B) is present in the terpolymer in an amount of from 1 to 98, preferably to 50 mole percent, based on the weight of the terpolymer and component (C) is present in an amount of between 1 to 50, preferably to 50 mole percent based on the molecular weight of the final terpolymer. It has been found that the terpolymer compositions thus prepared have a substantially increased boiling water shrinkage and show a great decrease in their tendency to flatspot when they are used as reinforcing fibers for vehicle tires.

In order to illustrate the invention and the advantages thereof with greater particularity, the following specific examples are given. It is to be understood that they are intended to be only illustrative and not limitative. Parts are given by weight unless otherwise indicated.

Example I A solution was prepared containing 85.5 parts (60 mole percent) of hexamethylenediammonium adipate, 18.36 parts (10 mole percent) of the hexamethylenediammonium salt of S-t-butylisophthalic acid, and 46.0 parts (30 mole percent) of hexamethylenediamrnonium ter ephthalate dissolved in 80 parts of water. This solution was added to a stainless-steel high pressure autoclave which had been previously purged of air by the use of purified nitrogen. The temperature and pressure Were slowly raised to 243 C. and 250 p.s.i.g. respectively, during which time there was the continuous removal of steamed condensate, At this point the pressure was gradually reduced to atmospheric over a -minute period and the polymer melt was allowed to equilibrate for minutes at 280 C. The polymer thus obtained had a melting point of approximately 265 C.

This finished polymer was melt spun directly from the autoclave through a single-hole spinneret yielding a monofilament transparent yarn possessing good textile properties. The tenacity of the yarn after being drawn over a hot pin (90 C.) was determined to be 4.91 grams per denier.

Example II A solution of 53.3 parts mole percent) of hexamethylenediammonium adipate, 43.1 parts (30 mole percent) of hexamethylenediammonium terephthalate and 51.7 parts (30 mole percent) of hexamethylenediammonium S-t-butylisophthalate dissolved in 80 parts of water was added to an autoclave and polymerized by the procedure set forth in Example I, The resulting transparent polymer had a melting point of approximately 240 C. Yarn spun from this polymer exhibited good textile properties.

Comparative tests were conducted to determine relative boiling water shrinkage in comparison to a conventional polyhexamethylene adiparnide (nylon 66) yarn. The yarns were exposed to boiling water for a period of 5 minutes and their lengths were measured both before and after exposure. The percent boiling water shrinkage is determined by the following formula:

length before exposure-length after exposure length before exposure 100=percent boiling water shrinkage The yarns prepared according to Examples I and II 1 4- flatspot severity and were found to have a significant reduction in the amount of fiatspot when compared to conventional polyhexamethylene adipamide reinforced tires. This reduction in fiatspot was maintained over a variety of conditions of temperature and humidity, thus eliminating the need for any additional additive to counteract the effect of atmospheric changes.

As many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not to be limited by the specific embodiments set forth herein but only by the claims which follow.

I claim:

1. A linear fiber-forming terpolyamide composed of (A) 1 to 98 mole percent, based on the molecular weight of the terpolyamide of units represented by the structure t i i H N-(OH2) NO(CHr)4C (B) 1 to 98 mole percent based on the molecular weight of the terpolyamide of units represented by the structure and (C) 1 to 50 mole percent, based on the molecular weight of the terpolyamide of units represented by the n H o 0 II II I T(CI'I2)e-1L C and (C) 20 to 50 mole percent, based on the molecular weight of the terpolyamide of units represented by the structure IIO 3. A textile fiber composed of the terpolyamide as defined in claim 1.

4. A textile fiber composed of the terpolyamide as defined in claim 2.

References Cited UNITED STATES PATENTS 2,715,620 8/1955 Carlston et al 260-78 2,913,433 11/1959 Wittbecker 260-78 2,918,454 12/1959 Graham 26078 3,012,994 12/1961 Bell ct al. 26078 WILLIAM H. SHORT, Primary Examiner.

HAROLD D. ANDERSON, Examiner. 

